Ive got a 1994 Prostar 205 the EFI model, got it second hand, its got 2100 hours on and the engine was just completely rebuilt after an overheat, and blown head gasket. Prior to the rebuild I had water in two of the cylinders, one on either side. The boat has mostly been used in salt water in recent times but I flush it after every use.

Since the rebuild the boat has been running nicely, I had the EFI removed and a quadrajet carb put on for ease of maintenance. I had the carb rebuilt as it had a flat spot around 3500 rpm. Since the rebuild on the carb I noticed the engine would hesistate at around 1500 rpm on the pull up. The revs would also drop dramatically when the boat was turned sharply.

This weekend before I went out I changed the bottom gasket on the carb for a thicker one and also put two new exhaust risers on as the old ones were quite worn from the salt use. The manifolds are quite new and didnt need replacing. I went to run the boat on the lawn to check for any leaks on the hoses etc and the boat wouldnt turn over. I checked the battery and connections and it was fine. I pulled all the plugs and to my dismay two of the cylinders were full of water... I turned the boat over and cleared them out, then ran the boat on the hose pipe with the plugs out of the effected cylinders, there was water vapour coming out of the plug holes. The oil was still fine but there was evidence of water vapour on the oil fill cap. I ran the boat on the lake for a very short time and it was struggling so we took it out.

I checked the oil later that evening and it was starting to look distinctly milky... I spoke to the mechanic who did the rebuild and he blamed the risers or the exhaust manifolds. The risers are brand new and im 90% on the manifolds being fine.

How can the boat be running fine one weekend and take such a rapid decline the next? The mechanics claimed the engine was completely rebuilt and was 'good as new' ive also noticed my transmission has started slipping slightly since the rebuild which has never happened before and was sliding out of gear violently when taking any kind of turn the last time out...

The boat is in South Africa and it is very hard to find reliable mechanics here, any advice would be much appreciated as I have no idea what to do next...

Thanks in advance

1redTA

10-28-2009, 11:54 AM

what type of motor is this

thatsmrmastercraft

10-28-2009, 12:30 PM

What is your source for water for the boat? If you are using a Fake-a-Lake, don't turn on the water until the engine starts. If you turn on the water before starting, you can have water backing up the exhaust and into any open exhaust valves.

Thrall

10-28-2009, 01:02 PM

What the guy above me said! If you turn ont he water for any length of time before starting the boat, I'm told water can get intot he cylinders thru the exh manifold.
Otherwise...another blown head gasket? Compression check can verify if you have comp in those cyliders.

Thomas205

10-28-2009, 01:31 PM

Its the 350 Chevy.

The cylinders had water in them after the boat was run in the lake as well and the sump oil turned milky pretty quickly after that. I did have the hose on for a short period before the engine fired so that may account for some of the water.

Jesus_Freak

10-28-2009, 01:43 PM

...Since the rebuild the boat has been running nicely, I had the EFI removed and a quadrajet carb put on for ease of maintenance...

Sorry you are having trouble.

Dumb question for ya...what was the benefit of going from TBI to carb?

Thomas205

10-28-2009, 01:48 PM

Its very hard to get parts here and service on the EFI and it was giving intermittent problems before, mechanic thought it would be a better bet to go with the carb...

DooSPX

10-28-2009, 02:38 PM

Its very hard to get parts here and service on the EFI and it was giving intermittent problems before, mechanic thought it would be a better bet to go with the carb...

I hope for your sake and whoever rides with you that the carb is a marine carb. with the j-tubes

russlars

10-28-2009, 02:46 PM

I don't have any advice on your engine problem, but as far as your transmission slipping, make sure that your fluid level is to the full mark. Test it while on the water and don't screw the dipstick in. Mine started slipping when it was just a little low on the dipstick because I had checked it on the trailer. Filled to the full mark and the slipping disappeared.

1redTA

10-31-2009, 12:32 AM

If it was the lt1 motor, they use diff head gaskets than a regular small block. This is from the reverse cooling in the heads. But if the heads gaskets were wrong your oil would look like a milk shake

JimN

10-31-2009, 01:06 AM

If the motor was reassembled using the old head bolts, that can cause problems. Also, if a good clicker type torque wrench wasn't used and a beam-type was, that is a major red flag for me. Beam type wrenches are very inaccurate and if the head/intake manifold bolts aren't torqued properly and in the correct sequence, it's not going to last long. Also, the motor in this configuration wasn't meant to run on that carb, so it should be tweaked (re-jetted, etc) to work with the motor.